Japanese Patent Application Laid-open No. 2000-291070 discloses a counterweight attachment and removal device that allows a counterweight to be removably attached to a rear end of a construction machine such as an excavator or a hydraulic crane. The counterweight attachment and removal device includes a bracket fixed to the rear end of the construction machine, a link with a base end thereof connected to the bracket such that the link is able to be elevated and lowered, a link cylinder that allows the link to be elevated or lowered, and a coupling unit connected to a leading end of the link via a hydraulic cylinder. The counterweight attachment and removal device allows the counterweight to be removably attached to the rear end of the construction machine by coupling the coupling unit to the counterweight and hanging the counterweight using the link and the link cylinder.
In the above-described counterweight attachment and removal device, when the counterweight is attached, coupling of the coupling unit to the counterweight fails unless the position of the coupling unit is aligned with the position of the counterweight when the link is lowered. Thus, in the above-described counterweight attachment and removal device, when the counterweight is attached, an operation is needed in which the position of the construction machine and the position of the counterweight are precisely adjusted in order to allow the coupling unit and the counterweight to be coupled together. This operation, particularly a widthwise adjustment operation for the construction machine and the counterweight, is very burdensome for an operator.